The invention relates generally to a system for dispensing fluids onto a substrate, and more particularly to a system having a manifold coupled to an array of adhesive dispensing nozzles for precisely dispensing hot melt adhesives supplied from a reservoir to the manifold by a metering gear pump.
The precise dispensing of hot melt adhesives and other fluids onto substrates is required in many applications. The manufacture of a variety of bodily fluid absorbing hygienic articles including disposable diapers and incontinence pads, sanitary napkins, patient underlays, and surgical dressings, for example, often requires bonding one or more layers of material, or substrates. These layers of material include, more specifically, a fluid impermeable, highly flexible thin film such as polypropylene or polyethylene onto which is adhered a highly absorbent pad often formed of a cellulose or plastic material covered by a non-woven fleece-like material. The fluid impermeable thin film, however, is extremely temperature sensitive, and hot melt adhesives have a tendency to deform the film and in some cases melt through the film. Materials bonded in other applications are similarly temperature sensitive.
It is known to dispense hot melt adhesive onto a substrate from nozzles that form thin fibers or stands of adhesive, which are nearly invisible to the naked eye and incapable of melting or distorting the substrate. In many applications, a plurality of adhesive dispensing nozzles are arranged generally in an elongated array directed toward the substrate, which is usually moved transversely relative to the nozzles. The hot melt adhesive is very often supplied to the nozzles from a reservoir by a gear pump including several fluid outlets, which simultaneously supply precisely metered amounts of adhesive to several corresponding fluid dispensing nozzles. U.S. Pat. No. 4,983,109 to Miller et al., for example, discusses several gear pumps interconnected by a common manifold assembly, including a pump manifold and a distribution manifold, to a plurality of nozzles wherein each gear pump simultaneously supplies precise amounts of adhesive to several corresponding nozzles. Each nozzle is specially configured for coupling with a corresponding adhesive supply conduit alone or in combination with a corresponding air supply conduit. A blocking plate configuration permits blocking alternatively the nozzle to prevent adhesive dispensing wherein the blocking plate recirculates adhesive back to the adhesive reservoir or back to the gear pump.
The inventors of the present invention recognize that controlling the temperature of compressed air combined with the hot adhesive in the nozzle is an effective means for controlling the adhesive dispensed by the nozzle. U.S. Pat. No. 4,983,109 to Miller et al., however, is not capable of independently controlling air temperature since compressed air is supplied through the common manifold assembly, which is maintained at a temperature required for adequately supplying and properly dispensing adhesive. The inventors of the present invention also recognize that it is desirable to recirculate adhesive as a means for dynamic pressure regulation, which may be required in the event adhesive flow through the one or more nozzles becomes obstructed, which occasionally occurs over time. Prior art hot melt adhesive applicators generally regulate pressure by limiting current to the motor that drives the gear pump, or by a clutch assembly that slips to limit load on the motor resulting from excessive fluid pressure. In U.S. Pat. No. 4,983,109 to Miller et al., adhesive is recirculated only when the nozzle is replaced by the specially configured blocking plate, which includes an internal passage interconnecting the adhesive supply conduit and the recirculation conduit. The blocking plate is however not intended to dispense adhesive or to regulate pressure in the event that an operational nozzle becomes obstructed.
In view of the discussion above, there exists a demonstrated need for an advancement in the art of fluid dispensing systems.
It is therefore an object of the invention to provide a novel system for dispensing fluids which overcomes problems in the prior art.
It is another object of the invention to provide a novel system for dispensing hot melt adhesives through a plurality of nozzles coupled to a manifold wherein hot melt adhesive is supplied to the nozzles, from a reservoir, by a common metering gear pump coupled to the manifold, which forms a metering gear-driven head.
It is also an object of the invention to provide a novel system usable for dispensing hot melt adhesives wherein the system includes adhesive dispensing nozzles for modifying dispensed adhesive with compressed air at a temperature controllable independently from an adhesive temperature.
It is another object of the invention to provide a novel system usable for dispensing hot melt adhesives including a plurality of adhesive dispensing nozzles coupled to a main manifold wherein fluid pressure is regulatable by recirculating adhesive toward the reservoir or toward the metering gear pump.
It is a further object of the invention to provide a novel system usable for supplying hot melt adhesives from a reservoir by a metering gear pump, dispensing hot melt adhesives through a plurality of adhesive dispensing nozzles coupled to a main manifold, and regulating fluid pressure by recirculating adhesive toward the reservoir through a recirculation manifold interchangeably coupled to the main manifold.
It is a further object of the invention to provide a novel system usable for dispensing hot melt adhesives, supplied from a reservoir by a metering gear pump, wherein the system includes a metering gear-driven head having a main manifold with a well for receiving the metering gear pump, and a common heating member for heating the main manifold and the metering gear pump.
It is still another object of the invention to provide a novel system usable for dispensing hot melt adhesives wherein the system includes a plurality of adjacently mounted main manifolds coupled to a plurality of fluid dispensing nozzles separated by substantially equal spacing therebetween and arranged along the plurality of adjacently mounted main manifolds.
It is a yet another object of the invention to provide a novel system usable for dispensing hot melt adhesives wherein the system includes a plurality of adjacently mounted main manifolds each having a second fluid supply conduit coupleable to a second fluid supply conduit of an adjacent main manifold.
These and other objects, features and advantages of the present invention will become more fully apparent upon consideration of the following Detailed Description of the Invention with the accompanying drawings, which may be disproportionate for ease of understanding, wherein like structure and steps are referenced by corresponding numerals and indicators.